The present invention is directed to apparatus for opening and closing doors, windows and the like such as a handle or lever for applying torque to door opening mechanisms. The handle includes a torque-limiting clutch subassembly which disengages the handle from the door opening mechanism at and above a predetermined torque.
Handles or levers for applying torque to door opening mechanisms to enable opening or closing a door are well known. However, excess torque can damage the handle, the door and/or the door opening mechanism, for example when excessive force is applied to the handle when the door opening mechanism is in a locked or secured position. Similarly, even when the door opening mechanism is unlocked, excess torque may damage the handle, the door and/or the door opening mechanism.
A variety of breakaway handle devices have attempted to solve these problems. For example, U.S. Pat. No. 1,910,125 includes a handle barrel which receives a longitudinally slidable sleeve. In operation, if excess torque is applied to the handle, the sleeve moves to a disengaged position where no torque is transmitted to the handle barrel. U.S. Pat. No. 2,273,632 shows a similar arrangement in which a moveable sleeve presses against and compresses a spring at a predetermined torque to disengage a tooth and notch connection between the handle and sleeve. Similarly, U.S. Pat. No. 3,314,708 includes a pair of opposed ball bearings which are normally biased into driving engagement with a sleeve by a spring-loaded plunger. Upon application of a predetermined torque, the ball bearings displace the plunger against the spring biasing force to disengage the balls from the sleeve.
These prior devices have attempted to solve the problem of preventing damage to handles, doors and door locks caused by excessive handle torque. However, a need exists for a simplified yet durable apparatus having the features of the present invention.
The present invention is based on a handle to transmit force through a spindle to a door opening mechanism. The handle is provided with a torque-limiting clutch subassembly to protect the handle against damage in the event that excess torque is applied to the handle, particularly, for example, when the door is locked. This object is inventively achieved in accordance with a slip clutch placed in working contact with the spindle within the handle. The slip clutch is provided with at least one notch to normally seat a spindle cross pin such that, upon application of a force, the handle normally rotates with the spindle through the coupling between the notch and the cross pin. However, upon the application of a predetermined force or torque, the cross pin will ride up out of the notch in the slip clutch thereby allowing the handle to rotate without rotating the spindle to prevent damage to the handle, the clutch subassembly, and/or the door opening mechanism.